Enzyme-Controlled Reactions Experiment

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Questions and Answers

Which variable should be changed when investigating enzyme-controlled reactions?

Volume of the enzyme solution

Only one variable at a time (correct)

Temperature of the solutions

Concentration of the substrate solution

What is the primary purpose of a negative control experiment in enzyme studies?

To demonstrate the effect of temperature on the enzyme

To confirm that the enzyme remains active during the experiment

To show that no reaction occurs without the substrate (correct)

To illustrate how enzymes work

In an enzyme-controlled reaction, how is the initial rate of reaction determined?

By finding the maximum temperature reached during the reaction

By calculating the average rate over the entire experiment

By drawing a tangent at zero on the graph of product versus time (correct)

By measuring the total volume of product produced

What molecules serve as the monomers of RNA?

Nucleotides with ribose sugar Signup and view all the answers

Why does the rate of enzyme-controlled reactions slow down over time?

Because enzyme-substrate complexes form more slowly as substrate is used Signup and view all the answers

Which of the following best describes the units of measurement for the rate of an enzyme-controlled reaction?

Cubic centimeters per minute Signup and view all the answers

Which substance is catalyzed by the enzyme catalase?

Hydrogen peroxide Signup and view all the answers

What component is NOT found in DNA nucleotides?

Ribose sugar Signup and view all the answers

What is the main difference between the induced fit model and the lock and key model of enzyme action?

The induced fit model implies that the active site changes shape upon substrate binding. Signup and view all the answers

What effect does an increase in temperature have on enzyme activity up to the optimum temperature?

It leads to an increase in the formation of enzyme-substrate complexes. Signup and view all the answers

Which of the following statements about enzyme denaturation is true?

Increasing pH levels above or below the optimum can lead to denaturation. Signup and view all the answers

What happens to the enzyme activity after it reaches the optimum temperature?

Denaturation occurs, altering the active site's shape. Signup and view all the answers

What characteristic do enzyme concentrations affect in a reaction?

The frequency of collisions between enzyme and substrate. Signup and view all the answers

What is indicated by the downward trend beyond the optimum temperature in the enzyme activity graph?

Enzyme activity decreases as the enzyme becomes denatured. Signup and view all the answers

Which condition would cause the shape of an enzyme's active site to change irreversibly?

Exceeding the optimum temperature. Signup and view all the answers

What occurs at the molecular level when the enzyme-substrate complex forms?

Strain is put on the substrate's bonds leading to a reaction. Signup and view all the answers

Study Notes

Investigating Enzyme-Controlled Reactions

Choose one variable to change at a time; control all other factors.
Use a gas syringe to measure the volume of oxygen produced by catalase over time and repeat the experiment with different temperatures.
Implement a negative control experiment to show no oxygen is produced without the active enzyme.

Control Variables

Volume, concentration of substrate and enzyme solutions.
Temperature and pH of solutions.
Use water baths for maintaining constant temperature during experiments.
Use buffer solutions to ensure consistent pH.

Calculating Rate of Reaction

Rate of reaction is calculated using the gradient of a line on a graph.
Initial rate is determined using a tangent drawn at the beginning of the curve.
The gradient of the tangent shows the rate of reaction at a specific point.
The initial rate will be highest because there are more enzyme-substrate interactions initially.

Explaining Rate of Reaction

Rate of reaction slows as the substrate is used up, resulting in fewer collisions.
The reaction stops when there is no substrate left.

### DNA and RNA Nucleotides

Deoxyribonucleic acid (DNA) contains deoxyribose as the pentose sugar.
Ribonucleic acid (RNA) contains ribose as the pentose sugar.
A nitrogenous base and a phosphate group are also present in both DNA and RNA nucleotides.

Enzymes

Proteins with a specific tertiary structure that act as biological catalysts.
Active site: Complementary to a specific substrate, speeding up reactions by lowering activation energy.
Location: Can be intracellular (inside cells) or extracellular (outside cells).
Importance: Crucial for Determining cell and organism structure.

Induced Fit Model

Replaced the Lock and Key Model, which proposed perfect enzyme-substrate complementarity.
Active site flexibility: The shape of the active site changes slightly upon substrate binding to become fully complementary.
Enzyme-Substrate Complex Formation: This complex puts stress on bonds or forms new bonds in the substrate, facilitating the reaction and lowering activation energy.

Temperature

Kinetic Energy: Higher temperature leads to increased enzyme and substrate kinetic energy, resulting in more frequent and successful collisions and enzyme-substrate complex formation.
Denaturation: Above the optimum temperature, enzymes become denatured. Excessive kinetic energy breaks hydrogen and ionic bonds between amino acid R groups, altering the active site shape and preventing substrate binding.
Reversibility: Low temperature effects on enzyme activity are reversible, but high temperature denaturation is irreversible.

pH

Denaturation: Enzymes are denatured both below and above the optimal pH.
Ionic and Hydrogen Bond Disruption: H⁺ (acidic) or OH⁻ (alkali) ions interfere with hydrogen and ionic bonds between amino acid R groups, changing the active site shape.

Enzyme or Substrate Concentration

Collision Frequency: Increasing either enzyme or substrate concentration increases the frequency of collisions between them, leading to more enzyme-substrate complexes.
Saturation: Eventually, all available active sites are filled, or substrate concentration becomes limiting, leading to a plateau in the reaction rate.
Graphs: The rate of reaction against temperature and pH is shown as bell-shaped curves, peaking at the optimum values. The curves demonstrate a maximum reaction rate that decreases as pH or temperature move away from the optimal levels. Denaturation is indicated by the downward trend in the curves beyond the optima.
Diagram: A diagram illustrates the enzyme-substrate interaction process, showcasing the formation of the enzyme-substrate complex, the induced fit concept, and the release of products.

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Description

This quiz explores the principles and techniques used in enzyme-controlled reactions, including how to manipulate variables and measure reaction rates. It covers the importance of controlling factors like temperature and pH, as well as utilizing graphs to calculate reaction rates. Test your understanding of fundamental concepts in biochemistry.